Frequencies for first 10,000 rows of ip_syph variable in natlterr2013 dataset :

   Syphilis |
596=f_ip_sy |
      ph) R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,077       10.77       10.77
          N |      8,544       85.44       96.21
          U |        376        3.76       99.97
          Y |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015